Stepless speed-change mechanism



De 4, 1956 N/oBoRU MIURA ETAL 2,772,580

sTEPLEss SPEED-CHANGE MECHANISM 3 Sheets-Sheet 1 Filed June 2. 1952 mwa/vrom oborw JIL lll/la' n/Mww/M TTYJ.

Dec- 4, 1956 NoBoRU MIURA Erm. 2,772,580

sTEPLEss SPEED-CHANGE MECHANISM Filed June 2, 1952 3 Sheets-Sheet 2 IMVENTORS .Ji/Z7 b ora Jau/raf lDem 4, 1956 NoBoRu MIURA ETAL 2,772,580

sTEPLEss SPEED-CHANGE MECHANISM Filed .June 2, 1952 s'sheets-sneet :s

INVLgNToR JVobprus Jaar@ Y 0 b, VMM JWM United States Patent-Q 2,112,580 sTEPLEss AsPEEDfCHA NGE MECHANISM Noboru Miura, Toyonaka City, and Hideo. Oketani, AArimagim, Japan, assignors of one-half to-Nobuki Yamamoto, Toyonaka City, and Seizaburo Ota, Nshinomiya City, J apanA l Application June z, 1952, senal'No. 291,132v priority, application Japan June 11,1951; z Claims. I(c1. 745675) This invention relates to a new stepless speed, changeA mechanism of torque control type, and the object of theinvention is to provide a mechanism to change ajspeed of a prime mover easily, smoothly, in a wide range and with an eieellent eciency through controlling the driving torque by means of an additional moment operated on a part of the mechanism.. We call this additional moment an inducing moment hereafter. t l

lAnother object of the invention is to provide themechanism in which, under constant driving power, the speed is controlled automatically in .inverse ratio toY the change of load, of the Amechanism having a constant characteristic,Vv

yWe obtain theseobjectsj by a peculiar arrangerr'ientV of planetary gear mechanisms and-a differential planetary gear. with a step-up gear under a peculiar condition of gear-ratios between eachgearingfas follows. ...,The peculiar condition of relative values among gear ratios above mentioned causing to keep a sun gear of saidv differential planetary gear always stand still, unrelated to the .speed .of the driver and the driven shaft enables to give ,the sun gearan inducinglmoment .which can be controlled easily by .means .of`applying the vforces ofV springs, iluidpressures or magnets or any other kindof force.

The control of the inducing moment causes the control; oftheldriving torque and the control of the driving power and consequently the control ofthe speed of the driven shaft, by a so-called equilibrium vcondition' ofthe power transmission.`

Figure 1 is a longitudinal section of a 'stepless speed-lE in Figure l';` 'Figure 8, 'the side ,view of an'example of theY 55 torque control 'device'. t Driver 1 is rotated by a prime mover, andplanetr gears- 4. and 5 which gear into'sun gear 3 xe'd'with a` key .to

drivenY shaft 2 inserted through the'driver gearlre's'pec` 'tively'.-into planet gear 7 and 8k which gearinto sun gear' .6'loose to driven shaft 2. 'ffSuh rgear 9; 1connected with sungerz6l by a hollow shaft iseloose' 4to AdrivenfshaftA 2, and planet gear and llwhich'gea'r into sun gear'91 gear respectively into planet gear 13 andf'1'4lwhich'sge'arli into sun gear'12 loose to driven shaft 2. Moreover, shaft 15 of planet gear 4, V:shaft .161ofplanet, gear 5, shaft 17 of planet gear 7, shaft 18 of planet gear 8, shaft 19 of planet gear 10, shaft :20 vof planet'v gearf11,""sliaft`21 of planet gear 13 and shaft 221of planet gear 14 are all supported to the sidewall of driver 1.V 'i One side wall of driver 1 is connected with driving shaft 23, another side wall of the same forms hollow shaft 24, and the both are supported by bearing respectively.. Hollow shaft 2 can be rotated freely ,around the Isaid 'armf34.

2 shaft 27 which is connected with sun gear 12 is loose to driven shaft 2 and hollow shaft 24 simultaneously, and gear 28 which is fixed to another end of hollow shaft 27 gears into gear 29, and gear 31* gears into gear 30. Gear 29 and 30 are connected and loose to shaft 32 supported in a fixed gear casing 33. The bevel type planet gears 35 and 36 provided Aat rotaryarm 34 fixed to kdriven The bevel type sun gear 37 which gears into the bevel type planet gea rs 35 and k36 ,is connected with gear 31, and loose to driven shaft 2. Another bevel type sun gear 38 which gears into planet gears 35 and 36 .is` also loose, to driven shaft 2. Thus the bevel type planet Yg'ears`35, 36 and the bevel type sun gears 37 and 38 :compose one set of the bevel type dilerentialplantary gearfAA torque control device is equipped at boss 39 connected withsun gear 3 8. Spring holders 42 whichprovide spring143 respectively are heldin the spaces between segments 40 By rotating hand-wheel 46, worm gear 44 is rotated through worm 45, accordingly one end of spring 43 is pressed through Vspring holder 42.by segment 41. And segment 40 at the otherend of spring holder 42 is pressed by spring 43, accordingly sun gear is given the inducing moment.

m--Revolution per minute of `driver 1. N-Revolution per minute. of driven shaft 2.

riz-Relative revolution per minute of planet gear 4: to.

sun gear 3 of the first train of the first set.

n2'-Relative revolution iper' minute of planet gea-r 7 to sun gear 6 of thesecond train of therst set. n-'Revolution Aper'r'ninute` of sun gear 6 of the second 'train ofthe rst set and of sun geai- 9 of the rst train of the' 'second' set;

'I ne- Relative revolutionper minute of planet gear 1( l to sun gear 9 of the''rst train of the secondset.

n44-4Relative 'revolution per minute of planet gearf-13 to sunge'ar 12"of thetsecond train ofthe second seti N1-Revolution per minute of sun gear 12 of the second Vtrain of the` second set-fand of 'spur' gear-28.(

"ge'ar' -37 o f "the bevel 'type 'dffeie'n'tial planetarygear.

tirsttrainfof thesecond set.

Vsecond' train of thesecond-set. -1

g 'ys-Gearfratio yof planetfgear4- to p lanetgear`7 of the- 'ys-Gear Lratioof planet .gea-r `lllto planet gear.13 ofi second setaA .1 'yr'.-eGeararatiolof spunzgea28fto jspur gear 29. n

And in ,the bevel type dite'rent'ial' planetary gear, there are the following relations:

For N". to be zero unrelated to and n1,` thefollowing conditions. should be simultaneously satisfied infthevForing sun gear 38, further explanation;l willy he; mentioned as follows. Y f f In general, the moments around. the-.shatt center 0f thesun gear and the.- planet gear in eachplanetary gear.

must be respectively under equilibriumfcondition.. Iny theV mechanism oi this invention,` ,the` equilibrium; condition is Vgiven, by driving torquejMn,A inducingl moment; Mc and load resisting momentqMf.; WhenaI planet gear offradius r2 'supported` in a driver rotatesaroundasun gear of radius r1 fixed to a drivengjsha'ftg-rthe cir-'leuniferential velocity V1 ofthe shaft` center of, thegplanet-V theY contactpoint of `the, sun gear with theplanetgear;

is 21rr1N; and When n1 N,. theabsolute instantaneous center of, thel revolution of the'..planet- .gear is; on thev straight line between thenshaft centeno the; sun: gear and the `contact point. o-the: sunagear'. withsth'e: planet;

gear. When the distance between this centera'ndi-.the shaft` center ofi theaplanet gearzis Yafytlfiej distance between: this center and the contact point of the sunrge'ar-with the planet gear Iis 'bytheA total load@ resisting momentn of.

total load resisting Vforce is R, vthere are the following-` relations:

F= Ml, 15,1%

Trl-tn n The power Mmm which is transmitted from prime mover to driver 1 shouldI be totally transmitted to driven shaft 2 by the equilibrium condition of power transmission if the mechanicalfetciency is-` 1,00%., formulated 2WMM1= Fifi: -RVFarMN F and total load resisting forceR obviously hold equilibrium condition, having the absolute instantaneous center :of the revolution of the planet gear as their axis. Thus when driving for'ce F s constant, by travelling of the absolute instantaneous` vt:enter.;ol the revolution vof the planet gear on the abovesaid straight line, the relations Fa=Rb and Vibi-Vz are always formed without any irrationality, even if total load resisting moment M which acts upon driven Shaft 2 may change, namely; even if R may change.v And two moments, drivingl torque and? total loadl resisting moment are'always held in equilib` rium condition, having thevabs'olte instantaneous 'center ofthe revolution ofz the planet gear a's'the shaftcenter;y

` As already mentioned, inthe mechanism-of this inv-en tion, considering equilibrium conditionf the moments around the shaft center of the sungea'r and ofthe planet gear of each planetary gea-r, equilibrium conditionis held by thevaction tof' three r'noments,A namely, driving torque, inducing'imoment and load resisting moment; -The load resistingmoment here-stated isV formulated ,=F(1"1`{r').A -F is load resisting force, and it'sabsolut'valuis always equalI to1 that of driving force F, Veven if4 total load resist-- ing force'R, namely, total load resisting moment'M maf,rr change. The loadl resisting force' ==F changes onlywhen driving force F changes. j So the conclusion maybe-i as follows. l Driving torque Mn, inducting montent' Mc; and load resisting moment "-'F(`r1={=r2) which act' aroundy the shaftcenter of the s'un gear and of the planet gearl of each planetary gear are all directly`u`fnrelatedA to' totaly load resisting moment M whichracts upon driven shaft 2, and are not influenced by' the change of M. Sogivingf the inducing moment Mc externally, the moments around' the shaft center of the sun gestrand of the planet' gear of eachplanetar'y `gear hold equilibrium conditionyaznd the driving torque' Mrt is controlled. The relation between inducing' moment and driving" torque Mn is formulated as follows,

th'ei motor; changes scarcely' againstlo'ad; .that is',` revol'u-l Y tiorn of theidriver ienerly oonstanta.: So if the" mechanical; efficiency` is .11.00%f5-froni'z-'tli'el equilibrium; conditionV 0E power:transrnis'sion;` f,

reyolutioriperminuteo driverr shaft -Mc or N -Mn The revolution of driven shaft changes in proportion to inducing moment Mc.

gradually from zero, N is also increased gradually from zero, and the so-called stepless speed-change can be which .acts upon exercised.

When inducing moment Mc is held constant, driving torque Mn is also constant.

That is, `the revolution of driven shaft changes in inverse ratio to total load resisting moment. In this case, when total load resisting moment M which acts upon driven shaft 2 changes, under the constant out-put characteristic, the revolution of driven shaft is changed in l.inverse ratio to M automatically, that is, the so-called In this formula, therevolution of motor s corresponding to the revolution of driven shaft in our mechanism,

and terminal voltage E'and load current Ia are respectively corresponding to inducing moment Mc and total load resisting moment M in our mechanism.

Thus by this invention, when sun gear 38 which is `always at rest is given the inducing moment through the control device, in case the totalload resisting force which acts upon driven shaft Z being constant, the revolution of driven shaft Z can be changed steplessly from zero to the optional number. When the inducing moment is held constant, in case the total load resisting force which acts upon driven shaft 2 being changed, the revolution of driven shaft 2 is changed in inverse ratio to total load resisting force automatically. Namely, the mechanism by our invention `has a peculiar character that speedchange can be exercised as the manner of the so-called automatic control type.

The abovementioned explanation is :all about two sets So when Mc is increased.

of planetary gear mechanism, one set of which consists l of two trains of planetary gear. However, optional sets may be exercised similarly. Especially the larger the number of the set, the largerV denominator in the formula (4) can be, that is, the smaller the ratio of Mc to Mn can be. So in the large power speed-change gear with large driving torque Mn, the larger the number of the set, the less the controlling torque Mc can be and easy speed-change is exercised.

As to the mechanical efficiency of the stepless speedchange mechanism in this invention, owing to its characteristics, the moments which act around the shaft center of the sun gear and the planet gear of each planetary gear are the inducing moment Mc, driving torque Mn and load resisting moment and as the total load resisting moment M does not act directly, the force which acts upon every part is small and the force which acts upon the teeth of gears Vis also small, even when M is considerably large and the revolution of driven shaft is small. So the power loss ofY every gear and every bearing is comparatively small. This is our excellent advantage which quite differs from the low efficiency condition in the conventional planetary gear with large reducing ratio in which one sun gear is lixed. Accordng to the stepless speed-change mechanism of this zero, while by the high speed revolution of the gears of the diiferential planetary gear and the step-up gear, there happens the power loss of gear and'others. On the contrary, when the revolution of vdriven shaft'comes very lclose to zero, the relative lmotion between the planet gear andthe sun gear of eachi planetary gear and the power loss become large, but the revolution of the vgears of the differential planetary gear and the step-up gear becomes almost zero, and the power loss of gears is nearly zero. So as a whole mechanical eiciency there is not so much dilerence between the former case and the latter. The mechanical eciency in the case of two sets in the driver is .thelhighest (88%) when the revolution of driven shaft is equal to the revolution of driver, and becomes small as the revolution of driven shaft comes toI zero. lAnd it becomes the lowest (81%) when N is nearly zero. It is an excellent character of this inventions mechanism'that the whole mechanical efticiency showsfavorable value within the broad range of. speed. Moreover, the invention makes it possible to start the revolution of the prime mover in an unloaded condition with inducing moment Mc at zero, and to accelerate` the revolution of the driven shaft from zero gradually by means of adding inducing moment gradually. l Consequently remarkable decrease. of the starting torque can be achieved and this serves as well for the clutching devicev between the prime mover and the driven shaft for no-load starting, and makes the device unnecessary. And the invention makes it possible to stop the driven shaft without stopping the prime mover by making the inducing moment Mc zero instantly. In addition, the mechanism is simple and can be light and of small type. The speed-change operation is very easy, and automatic controlling of revolution can be performed by its constant out-put characteristic. This invention offers an ideal stepless speed-change mechanism owing to these excellent faculties which suflce the necessary conditions of the speed change of all means of communi- Y cation. Moreover, as one of the special characteristic of this invention, being able to hold the driving torque Mn constant notwithstanding the change of total load resisting moment M by holding the inducing moment Mc constant makes the load condition of the internal combustion engine of the means of communication to be controlled always in the highest thermal efciency. This load condition is always held favorable unrelated to the change of running resistance as long as inducing mo ment Mc is held constant, resulitng in the economy of the fuel consumed. When used in the general production machine this mechanism shows also an excellent quality and effect, and proves to be truly an elective, adequate and unique industrial invention.

It is the intention to cover all equivalents of the invention above described together with all modifications and variations thereof that are within'the scope of the appended claims.

We claim:

l. A torqu'e control type stepless speed change mechafixed to the end of said driver shaft within the driven and engaged with the first planet gear of the first pair of said pairs of planet gears, a plurality of sun gears loosely mounted on said driven shaft one connecting each of said pairs of planet gears by engagement with the second planet-.gearfof .one pai-ref :planetgears and '-thefirst. planet -geanof the next -adjacent -par-of y.planet gears; ax further sun-gearloosely mounted on said-driven shaft engaged with the Vsecond planet gear 4of the-last of -said'` pairs of planet,` gearsya projection fixed to said driven shaft, `a diierential planet gear rotatably mounted 0n said pro- `jection .and ygeared `to said 'further sun gear by ai gear .`train, a reaction., gear -rotatably mounted on said driven 4shaft and engaged with Ysaid-'differential Iplanetary gear, means to rotate said reaction gear to impart a torque to said differential planet gear, the relative sizesof said sun gears; planet gears and differential planet gear being sch `that aptorquelapplied t0 Vsid' differential planetvgear c'hange`s`the relative speeds of said 'driven shaft' ahd" driver stepless'ly.

"with each other, a ysun'geariixed tothe -end of said driven shaft Within the driver easingy and engaged witlithi-fist planet gear of the first pair'of saidfpairsofplanet gears, a plurality of sun-gearsl loosely inountedonl said"vvv drive shaft, oneeonnecti'ng--ech' of-saidpairs ofpla'net gears 8 by engagement with the second planet gear `offone pair 0f planet gears and the first planet gear of the next adjacent pair of planet'g`e`ars,-fa further sun gear loosely mounted 0n saidw'driven shaft engaged'with the -seeond :planet-gear of thelast of vsaid pairs of planet gears and having a'hollowwshaft extendingwitlrin said driver cas- -i'ngI hollow shaft;l a sun gear on the end of said hollow shaft, a step-up gear mounted on said gear casing con- Nn'eeted with said sun gear, afprojection lixed to said driven shaft, a differential planetary gear rotatably mounted on said projection, an intermediary sun gear loosely mounted 0n said driven shaftrengaged with said step-up gear and said dilerential gear, a reaction gear rotatably mountv-fed onrsaididriv'en shaft-and' engagedv with said dilfereritial planetfgear, a means to rotate said reaction gear to irnpart a torque "to saiddiierentialplanet gear, the'relative sizes ofl said sun gears,'planet gears andv differential planet gear-being such that a'torque applied tol said differential planet lgear changes the relativel speeds .of said ldriven sh-aft and driver' separately.

f References Cited in theiile of this patent UNITED STATES PATENTS 1,300,118 Carter et a1. Apr. 8,- 1919 1,590,902 Natisch June 29, 1926 2,154,710 Thoma 2 Apr. 18, 1939 2,269,734 Powell Jan. 13, 1942 4"FOILEIGN PATENTS '718,202 France Jan. 21, 1932 

